Lithographic apparatus and device manufacturing method

ABSTRACT

Apparatus and methods for compensating for the movement of a substrate in a lithographic apparatus during a pulse of radiation include providing a pivotable mirror configured to move a patterned projection beam incident on the substrate in synchronism with the substrate.

FIELD OF THE INVENTION

The present invention relates to lithographic projection apparatus andmethods.

BACKGROUND

The term “programmable patterning structure” as here employed should bebroadly interpreted as referring to any configurable or programmablestructure or field that may be used to endow an incoming radiation beamwith a patterned cross-section, corresponding to a pattern that is to becreated in a target portion of a substrate; the terms “light valve” and“spatial light modulator” (SLM) can also be used in this context.Generally, such a pattern will correspond to a particular functionallayer in a device being created in the target portion, such as anintegrated circuit or other device (see below). Examples of suchpatterning structure include:

A programmable mirror array. One example of such a device is amatrix-addressable surface having a viscoelastic control layer and areflective surface. The basic principle behind such an apparatus is that(for example) addressed areas of the reflective surface reflect incidentlight as diffracted light, whereas unaddressed areas reflect incidentlight as undiffracted light. Using an appropriate filter, theundiffracted light can be filtered out of the reflected beam, leavingonly the diffracted light behind; in this manner, the beam becomespatterned according to the addressing pattern of the matrix-addressablesurface. An array of grating light valves (GLVs) may also be used in acorresponding manner, where each GLV may include a plurality ofreflective ribbons that can be deformed relative to one another (e.g.,by application of an electric potential) to form a grating that reflectsincident light as diffracted light. A further alternative embodiment ofa programmable mirror array employs a matrix arrangement of very small(possibly microscopic) mirrors, each of which can be individually tiltedabout an axis by applying a suitable localized electric field, or byemploying piezoelectric actuation means. For example, the mirrors may bematrix-addressable, such that addressed mirrors will reflect an incomingradiation beam in a different direction to unaddressed mirrors; in thismanner, the reflected beam is patterned according to the addressingpattern of the matrix-addressable mirrors. The required matrixaddressing can be performed using suitable electronic means. In both ofthe situations described hereabove, the patterning structure cancomprise one or more programmable mirror arrays. More information onmirror arrays as here referred to can be gleaned, for example, from U.S.Pat. Nos. 5,296,891 and 5,523,193 and PCT Patent Application Nos. WO98/38597 and WO 98/33096, which documents are incorporated herein byreference. In the case of a programmable mirror array, the said supportstructure may be embodied as a frame or table, for example, which may befixed or movable as required.

A programmable LCD array. An example of such a construction is given inU.S. Pat. No. 5,229,872, which is incorporated herein by reference. Asabove, the support structure in this case may be embodied as a frame ortable, for example, which may be fixed or movable as required.

It should be appreciated that where pre-biasing of features, opticalproximity correction features, phase variation techniques, and/ormultiple exposure techniques are used, the pattern “displayed” on theprogrammable patterning structure may differ substantially from thepattern eventually transferred to the substrate or layer thereof.

Lithographic projection apparatus can be used, for example, in themanufacture of integrated circuits (ICs), flat panel displays, and otherdevices involving fine structures. In such a case, the programmablepatterning structure may generate a circuit pattern corresponding to anindividual layer of, for example, the IC, and this pattern can be imagedonto a target portion (e.g., comprising one or more dies and/orportion(s) thereof) on a substrate (e.g., a glass plate or a wafer ofsilicon or other semiconductor material) that has been coated with alayer of radiation-sensitive material (e.g., resist). In general, asingle wafer will contain a whole matrix or network of adjacent targetportions that are successively irradiated via the projection system(e.g., one at a time).

The lithographic projection apparatus may be of a type commonly referredto as a step-and-scan apparatus. In such an apparatus, each targetportion may be irradiated by progressively scanning the mask patternunder the projection beam in a given reference direction (the “scanning”direction) while synchronously scanning the substrate table parallel oranti-parallel to this direction. Since, in general, the projectionsystem will have a magnification factor M (generally <1), the speed V atwhich the substrate table is scanned will be a factor M times that atwhich the mask table is scanned. A projection beam in a scanning type ofapparatus may have the form of a slit with a slit width in the scanningdirection. More information with regard to lithographic devices as heredescribed can be gleaned, for example, from U.S. Pat. No. 6,046,792,which is incorporated herein by reference.

In a manufacturing process using a lithographic projection apparatus, apattern (e.g., in a mask) is imaged onto a substrate that is at leastpartially covered by a layer of radiation-sensitive material (e.g.,resist). Prior to this imaging procedure, the substrate may undergovarious other procedures such as priming, resist coating, and/or a softbake. After exposure, the substrate may be subjected to other proceduressuch as a post-exposure bake (PEB), development, a hard bake, and/ormeasurement/inspection of the imaged features. This set of proceduresmay be used as a basis to pattern an individual layer of a device (e.g.,an IC). For example, these transfer procedures may result in a patternedlayer of resist on the substrate. One or more pattern processes mayfollow, such as deposition, etching, ion-implantation (doping),metallization, oxidation, chemo-mechanical polishing, etc., each ofwhich may be intended to create, modify, or finish an individual layer.If several layers are required, then the whole procedure, or a variantthereof, may be repeated for each new layer. Eventually, an array ofdevices will be present on the substrate (wafer). These devices are thenseparated from one another by a technique such as dicing or sawing,whence the individual devices can be mounted on a carrier, connected topins, etc. Further information regarding such processes can be obtained,for example, from the book “Microchip Fabrication: A Practical Guide toSemiconductor Processing,” Third Edition, by Peter van Zant, McGraw HillPublishing Co., 1997, ISBN 0-07-067250-4.

The term “projection system” should be broadly interpreted asencompassing various types of projection system, including refractiveoptics, reflective optics, catadioptric systems, and micro lens arrays,for example. It is to be understood that the term “projection system” asused in this application simply refers to any system for transferringthe patterned beam from the programmable patterning structure to thesubstrate. For the sake of simplicity, the projection system mayhereinafter be referred to as the “lens.” The radiation system may alsoinclude components operating according to any of these design types fordirecting, shaping, reducing, enlarging, patterning, and/or otherwisecontrolling the projection beam of radiation, and such components mayalso be referred to below, collectively or singularly, as a “lens.”

Further, the lithographic apparatus may be of a type having two or moresubstrate tables (and/or two or more mask tables). In such “multiplestage” devices the additional tables may be used in parallel, orpreparatory steps may be carried out on one or more tables while one ormore other tables are being used for exposures. Dual stage lithographicapparatus are described, for example, in U.S. Pat. No. 5,969,441 and PCTApplication No. WO 98/40791, which documents are incorporated herein byreference.

The lithographic apparatus may also be of a type wherein the substrateis immersed in a liquid having a relatively high refractive index (e.g.,water) so as to fill a space between the final element of the projectionsystem and the substrate. Immersion liquids may also be applied to otherspaces in the lithographic apparatus, for example, between the mask andthe first element of the projection system. The use of immersiontechniques to increase the effective numerical aperture of projectionsystems is known in the art.

In the present document, the terms “radiation” and “beam” are used toencompass all types of electromagnetic radiation, including ultravioletradiation (e.g., with a wavelength of 365, 248, 193, 157 or 126 nm) andEUV (extreme ultra-violet radiation, e.g., having a wavelength in therange 5-20 nm), as well as particle beams (such as ion beams or electronbeams).

In presently known lithographic projection apparatus using programmablepatterning structure, the substrate table is scanned in the path of thepatterned projection beam (e.g., below the programmable patterningstructure). A pattern is set on the programmable patterning structureand is then exposed on the substrate during a pulse of the radiationsystem. In the interval before the next pulse of the radiation system,the substrate table moves the substrate to a position as required toexpose the next target portion of the substrate (which may include allor part of the previous target portion), and the pattern on theprogrammable patterning structure is updated if necessary. This processmay be repeated until a complete line (e.g., row of target portions) onthe substrate has been scanned, whereupon a new line is started.

During the small but finite time that the pulse of the radiation systemlasts, the substrate table may consequently have moved a small butfinite distance. Previously, such movement has not been a problem forlithographic projection apparatus using programmable patterningstructure, e.g., because the size of the substrate movement during thepulse has been small relative to the size of the feature being exposedon the substrate. Therefore the error produced was not significant.However, as the features being produced on substrates become smaller,such error becomes more significant. U.S. Publication Application No.2004/0141166 proposes one solution to this problem.

Although specific reference may be made in this text to the use of theapparatus according to an embodiment of the invention in the manufactureof ICs, it should be explicitly understood that such an apparatus hasmany other possible applications. For example, it may be employed in themanufacture of integrated optical systems, guidance and detectionpatterns for magnetic domain memories, liquid-crystal display (LCD)panels, thin-film magnetic heads, thin-film-transistor (TFT) LCD panels,printed circuit boards (PCBs), DNA analysis devices, etc. The skilledartisan will appreciate that, in the context of such alternativeapplications, any use of the terms “wafer” or “die” in this text shouldbe considered as being replaced by the more general terms “substrate”and “target portion”, respectively.

SUMMARY

A device manufacturing method according to an embodiment of theinvention includes using a radiation system to provide a pulsed beam ofradiation, and using a patterning structure to pattern the pulsed beamaccording to a desired pattern. The patterned beam is projected onto atarget portion of a layer of radiation-sensitive material that at leastpartially covers a substrate, and the substrate is moved relative to theprojection system. A path of the projected beam relative to theprojection system is altered during at least one pulse of the pulsedbeam, such that a cross-section of the projected beam in a planeparallel to a surface of the target portion is substantially stationaryrelative to the substrate during the at least one pulse. Severalapparatus that may be applied to perform such a method, and devicesmanufactured thereby, are also disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

Exemplary embodiments of the invention will now be described, by way ofexample only, with reference to the accompanying schematic drawings inwhich:

FIG. 1 depicts a lithographic projection apparatus according to anembodiment of the invention;

FIG. 2 schematically depicts a structure configured to move thepatterned projection beam according to an embodiment of the presentinvention;

FIG. 3 schematically depicts a structure configured to move thepatterned projection beam after a partial movement of the structure;

FIG. 4 schematically depicts a structure configured to move thepatterned projection beam after further movement of the structure; and

FIG. 5 schematically depicts a control loop for the structure.

In the Figures, corresponding reference symbols indicate correspondingparts.

DETAILED DESCRIPTION

Embodiments of the invention include, for example, methods and apparatusthat may be used to reduce errors caused by movement of the substrateduring a pulse of the radiation system.

FIG. 1 schematically depicts a lithographic projection apparatus 1according to a particular embodiment of the invention. The apparatuscomprises:

A radiation system configured to supply (e.g., having structure capableof supplying) a projection beam of radiation. In this particularexample, the radiation system Ex, IL, for supplying a projection beam PBof radiation (e.g., UV or EUV radiation) also comprises a radiationsource LA;

A programmable patterning structure PPM (e.g., a programmable mirrorarray) configured to apply a pattern to the projection beam. In general,the position of the programmable patterning structure will be fixedrelative to projection system PL. However, it may instead be connectedto a positioning structure configured to accurately position it withrespect to projection system PL;

An object table (substrate table) WT configured to hold a substrate. Inthis example, substrate table WT is provided with a substrate holder forholding a substrate W (e.g., a resist-coated semiconductor wafer) and isconnected to a positioning structure PW for accurately positioning thesubstrate with respect to projection system PL and (e.g.,interferometric) measurement structure IF, which is configured toaccurately indicate the position of the substrate and/or substrate tablewith respect to projection system PL; and

A projection system (“lens”) PL (e.g., a quartz and/or CaF₂ lens system,a catadioptric system comprising lens elements made from such materials,and/or a mirror system) configured to project the patterned beam onto atarget portion C (e.g., comprising one or more dies and/or portion(s)thereof) of the substrate W. The projection system may project an imageof the programmable patterning structure onto the substrate.

As here depicted, the apparatus is of a reflective type (e.g., has areflective programmable patterning structure). However, in general, itmay also be of a transmissive type (e.g., with a transmissiveprogrammable patterning structure) or have aspects of both types.

The source LA (e.g., a mercury lamp, an excimer laser, an electron gun,a laser-produced plasma source or discharge plasma source, or anundulator provided around the path of an electron beam in a storage ringor synchrotron) produces a beam of radiation. This beam is fed into anillumination system (illuminator) IL, either directly or after havingtraversed a conditioning structure or field, such as a beam expander Ex,for example. The illuminator IL may comprise an adjusting structure orfield AM for setting the outer and/or inner radial extent (commonlyreferred to as σ-outer and σ-inner, respectively) of the intensitydistribution in the beam, which may affect the angular distribution ofthe radiation energy delivered by the projection beam at, for example,the substrate. In addition, the apparatus will generally comprisevarious other components, such as an integrator IN and a condenser CO.In this way, the beam PB impinging on the programmable patterningstructure PPM has a desired uniformity and intensity distribution in itscross-section.

It should be noted with regard to FIG. 1 that the source LA may bewithin the housing of the lithographic projection apparatus (as is oftenthe case when the source LA is a mercury lamp, for example), but that itmay also be remote from the lithographic projection apparatus, theradiation beam which it produces being led into the apparatus (e.g.,with the aid of suitable direction mirrors); this latter scenario isoften the case when the source LA is an excimer laser. The currentinvention and claims encompass both of these scenarios. In a typicalsource LA, there are a number of effects that can result in imagingerrors in lithographic imaging processes. In an embodiment wherein thesource LA provides pulsed radiation, for instance, these may includepulse amplitude variation, pulse-width variation, and pulse-to-pulsevariation, also known as jitter.

The beam PB subsequently intercepts the programmable patterningstructure PPM, which may be held on a mask table (not shown). Havingbeen selectively reflected by (alternatively, having traversed) theprogrammable patterning structure PPM, the beam PB passes through theprojection system PL, which focuses the beam PB onto a target portion Cof the substrate W. In the embodiment of FIG. 1, a beam splitter BSserves to direct the beam to the patterning structure PPM, while alsoallowing it to pass through to the projection system PL, howeveralternate geometries are within the scope of the present invention.

With the aid of the positioning structure (and interferometric measuringstructure IF), the substrate table WT can be moved accurately, e.g., soas to position different target portions C in the path of the beam PB.Where used, a positioning structure for the programmable patterningstructure PPM can be used to accurately position the programmablepatterning structure PPM with respect to the path of the beam PB (e.g.,after a placement of the programmable patterning structure PPM, betweenscans, and/or during a scan).

In general, movement of the object table WT may be realized with the aidof a long-stroke module (e.g., for coarse positioning) and ashort-stroke module (e.g., for fine positioning), which are notexplicitly depicted in FIG. 1. A similar system may be used to positionthe programmable patterning structure PPM. It will be appreciated that,to provide the required relative movement, the projection beam mayalternatively or additionally be movable, while the object table and/orthe programmable patterning structure PPM may have a fixed position.Programmable patterning structure PPM and substrate W may be alignedusing substrate alignment marks P1, P2 (possibly in conjunction withalignment marks of the programmable patterning structure PPM).

The depicted apparatus can be used in several different modes. In onescan mode, the mask table is movable in a given direction (the so-called“scan direction,” e.g., the y direction) with a speed v, so that theprojection beam PB is caused to scan over a mask image. Concurrently,the substrate table WT is simultaneously moved in the same or oppositedirection at a speed V=Mv, in which M is the magnification of the lensPL (typically, M=¼ or ⅕). In some embodiments, the demagnification issignificantly smaller than 1, for example smaller than 0.3, smaller than0.1, smaller than 0.05, smaller than 0.01, smaller than 0.005, orsmaller than 0.0035. Likewise, it is contemplated that M may be largerthan 0.001, or may be within a range between 0.001 and the foregoingupper limits. In this manner, a relatively large target portion C can beexposed, without having to compromise on resolution.

In another mode, the mask table is kept essentially stationary holding aprogrammable patterning structure, and the substrate table WT is movedor scanned while a pattern imparted to the projection beam is projectedonto a target portion C. In this mode, generally a pulsed radiationsource is employed and the programmable patterning structure is updatedas required after each movement of the substrate table WT or in betweensuccessive radiation pulses during a scan. This mode of operation can bereadily applied to lithography that utilizes programmable patterningstructure, such as a programmable mirror array as referred to above.

Combinations and/or variations on the above-described modes of use orentirely different modes of use may also be employed.

An apparatus as depicted in FIG. 1 may be used, for example, in thefollowing manner. In pulse mode, the programmable patterning structurePPM is kept essentially stationary, and the entire pattern is projectedonto a target portion C of the substrate using a pulsed radiationsource. The substrate table WT is moved with an essentially constantspeed such that the projection beam PB is caused to scan a line acrossthe substrate W. The pattern on the programmable patterning structurePPM is updated as required between pulses of the radiation system, andthe pulses are timed such that successive target portions C are exposedat the required locations on the substrate W. Consequently, theprojection beam PB can scan across the substrate W to expose thecomplete pattern for a strip of the substrate. Such a process may berepeated until the complete substrate W has been exposed line by line.Different modes may also be used.

Because of the relative motion of the substrate table during imaging,changes in the time domain at the light source LA map to changes in thespatial domain at the substrate table WT. This results in two maineffects. First, when there is a change in the pulse interval, there is achange in imaged position on the substrate. For example, a pulseinterval that is slightly longer than average results in a greaterdistance between imaged portions of the wafer. Second, a change in pulseduration results in a blurring effect, as a longer or shorter portion ofthe wafer traverses the image field during the pulse.

In order to account for the movement of the substrate table WT, a devicein accordance with an embodiment of the present invention may include amirror 10 forming a part of the lens PL, as shown in FIG. 2. Inparticular, the mirror 10 is beneficially located proximate a pupil ofthe lens PL or at a conjugate plane thereof. Though FIG. 2 shows thelens PL as a two-part device, with the mirror 10 bisecting the lens PL,that is not, in general, a requirement of embodiments of the presentinvention. To the contrary, the specific arrangement of the lens PL maybe varied as required according to other desired imagingcharacteristics. As will be appreciated, the mirror 10 should besubstantially planar, though in practice it may be possible to allow forsome curvature, whereby a portion of the optical power of the lenssystem resides in the mirror.

An actuator, or group of actuators, 12 is positioned to move the mirror10 during an imaging operation. In a particular embodiment, the actuator12 is arranged to rotate the mirror 10 about a small angle at arelatively high frequency, and with a small displacement. The pivotablemirror 10 is supported by a support assembly 22. A frequency ofoscillation timing of the mirror 10 substantially corresponds to aresonance frequency of the mirror 10 and support assembly 22. Supportassembly 22 includes counter-mass 25, constructed and arranged toisolate forces produced by the actuator 12 from a remaining part of theapparatus. Actuator 12 included multiple motors 29, and is constructedand arranged to impart rotational forces on the mirror 10.

The system of FIG. 2 is shown as having a 1:1 magnification ratio, and arelatively large rotation of the mirror 10. As a result, the focal point14 at the image plane 16 is displaced from the optical axis 18 by arelatively large amount d. In practice, there may be a significantde-magnification, and the tilt of the mirror 10 will be quite small, sothat the displacement may then be quite small. In particular, thedisplacement of the image should correspond substantially to a distancetraversed by the substrate table over the duration of a single pulse ofthe radiation source.

By way of example, a displacement at the mirror 10 of 1 nm at theposition of a marginal ray maps to a displacement at the image plane 16of 1/NA, where NA is the numerical aperture of the lens PL. Likewise,the rotational change of the mirror a′ [in rad/s] translates over thediameter of the beam at the pupil D [in m], into a velocity v at waferlevel [in m/s]: v=a′D/(2 NA).

FIGS. 3 and 4 illustrate schematically later times in a single scan, assuccessive pulses are imaged onto the focal plane. In FIG. 3, the mirror10 has rotated through to its zero-crossing, and the focal point 14 isaligned with the optical axis 18. FIG. 4 continues the motion and thefocal point 14 is once more displaced from the optical axis 18, in adirection opposite to its initial displacement of FIG. 2.

In a typical lithographic apparatus, the source LA may have a pulserepetition rate on the order of 1-10 kHz. As a result, it is useful toensure that the mirror 10 can be adequately vibrated in phase with thatfrequency, meaning that the actuator or actuators 12 should be adaptedfor high frequency operation. Furthermore, if the mirror 10 is designedso that, along with its associated mounting structure, it has a resonantfrequency that is equal to the pulse frequency of the source LA, energyrequired to move the mirror will be minimized. This has the additionaleffect that the load on the actuators and consequently the deformationload on the mirror 10 is minimized.

In furtherance of the goal of matching the frequency of the vibration ofthe mirror 10 with the pulse frequency of the source LA, it is possibleto include a sensor 30 that is connected in a control loop with themirror 10 and its actuators 12. For synchronization of the movement ofthe mirror to the laser pulse frequency, different methods may be used.By way of example, a signal from the sensor 30 on the vibrating mirrorcan be used to trigger the laser pulse, or a phase locked loop systemwhere the laser frequency is fixed to the average resonant frequency ofthe mirror while the controller adjusts the mirror frequency and phaseto the fixed laser frequency.

In addition to ensuring that the frequency of vibration of the mirror 10is synchronized with the frequency of the source LA, it may bebeneficial to ensure that the amplitude A of the rotational velocity ofthe mirror 10 corresponds to a scan speed of the substrate table.

Further by way of example, in a typical system, the actual values may beas follows. The scan speed may be on the order of 10 mm/s, NA=1, andD=20 mm. This leads to a′=1 rad/s at the zero-crossing of a sinusoidalrotational movement of the mirror 10. Given that for a sinusoidalmovement a=A sin(2π t υ), so the time derivative equals: a′=A 2 π υcos(2 π t υ). At t=0 this becomes: a′=A 2 π υ so that for a 1 kHzvibration, the amplitude of the movement of the mirror becomes: A=0.16mrad.

The choice of a sinusoidal rotational motion of the mirror may allow forsome useful effects. In particular, by choosing a portion of the motionclose to the zero crossing to coincide with the imaging pulse, and asmall amplitude, the sinusoidal motion is substantially linear.Furthermore, the gradual deceleration and acceleration at the end pointsof the motion reduce stresses on the mirror, which, if unchecked, couldlead to deformations of the mirror over time.

The mirror may also be coupled to one or more balance masses. Thebalance masses are configured to take up and isolate forces produced bythe actuator in vibrating the mirror. In particular, the masses areconfigured to be freely movable in a direction opposite to the forcesgenerated by the actuator, conserving momentum of the balancemass-mirror system and thereby reducing forces introduced into otherportions of the lithographic apparatus.

Embodiments of the present invention can provide the ability to increasepulse time as a result of decreasing blur associated with movement ofthe substrate table. One useful result of increased pulse time is theability to reduce peak intensity, without reducing a total energy perpulse, thereby reducing potential damage to optical components. Anotheruseful result is that the number of temporal modes may increase, therebyreducing speckle in the optical system. Finally, longer pulse times mayallow for the ability to truncate individual pulses, thereby allowingfor pulse-to-pulse dose control adjustments.

Errors caused by the movement of the substrate relative to theprojection system during a pulse of radiation may be reduced byproviding one or more apparatus to shift the patterned projection beamin synchronism with the movement of the substrate during a pulse ofradiation, which may allow the projection beam to remain more accuratelyaligned on the substrate. Alternative structures that may be applied toshift the patterned projection beam are also within the scope of theinvention.

It may be desirable to move the substrate at a constant velocityrelative to the projection system during a series of pulses of theradiation system and the intervals in between the pulses. An apparatusas described herein may then be used to move the patterned projectionbeam in synchronism with the movement of the substrate for the durationof at least one pulse of the radiation system. Having the substratemoving at a constant velocity may reduce the complexity of the substratetable and the positional drivers associated with it, and moving thepatterned projection beam in synchronism with the movement of thesubstrate may reduce consequent errors.

The patterned projection beam may be moved in synchronism with themovement of the substrate during a plurality of pulses. Such anarrangement may enable the images of the programmable patterningstructure to be projected onto the same part of the substrate aplurality of times. This technique may be done, for example, if theintensity of the pulse of the patterned projection beam is notsufficient to produce a complete exposure on the substrate. Moving thepatterned projection beam in synchronism with the substrate may reducethe occurrence of overlay errors between subsequent exposures of thepattern on the substrate.

Successive patterns on the programmable patterning structure that areexposed on the substrate by each pulse may be different. For example,corrections may be made in subsequent pulses to offset errors in a firstpulse. Alternatively, changes in the pattern may be used to produce grayscale images for some of the features (for example, by only exposingthose features for a proportion of the total number of pulses imagedonto a given part of the substrate).

Additionally (or alternatively) the intensity of the patternedprojection beam, the illumination of the programmable patterning means,and/or the pupil filtering may be changed for one or more of the pulsesof the radiation system that are projected onto the same part of thesubstrate. This technique may be used, for example, to increase thenumber of gray scales that may be generated using the techniquedescribed in the preceding paragraph or may be used to optimizedifferent exposures for features oriented in different directions.

While specific embodiments of the invention have been described above,it will be appreciated that the invention as claimed may be practicedotherwise than as described. For example, although use of a lithographyapparatus to expose a resist on a substrate is herein described, it willbe appreciated that the invention is not limited to this use, and anapparatus according to an embodiment of the invention may be used toproject a patterned projection beam for use in resistless lithography.Thus, it is explicitly noted that the description of these embodimentsis not intended to limit the invention as claimed.

1. A lithographic projection apparatus comprising: a programmablepatterning structure configured to pattern a radiation beam generated bya radiation system according to a desired pattern and generate apatterned radiation beam; a projection system configured to project thepatterned radiation beam onto a target portion of a substrate; apositioning structure configured to move the substrate relative to theprojection system during exposure by the patterned radiation beam; asingle-faceted oscillatingly pivotable mirror configured to move thepatterned radiation beam relative to the projection system during atleast one pulse of the radiation beam; and an actuator configured tooscillatingly pivot the mirror according to an oscillation timing thatsubstantially corresponds to a pulse frequency of the radiation system,whereby the patterned radiation beam is scanned in synchronism with themovement of the substrate during the at least one pulse.
 2. Theapparatus of claim 1, wherein the actuator is controlled by a controllerand wherein the controller, actuator and radiation system areinterconnected in a control loop arrangement and wherein the controlloop is configured to maintain synchronism between oscillation of themirror and pulses of the radiation system.
 3. The apparatus of claim 1,wherein the pivotable mirror is supported by a support assembly, and afrequency of the oscillation timing substantially corresponds to aresonance frequency of the mirror and its support assembly.
 4. Theapparatus of claim 3, wherein the support assembly further comprises theactuator.
 5. The apparatus of claim 4, wherein the support assemblyfurther comprises at least one counter-mass, constructed and arranged toisolate forces produced by the actuator from a remaining part of theapparatus.
 6. The apparatus of claim 1, wherein the actuator comprises aplurality of motors, constructed and arranged to impart rotationalforces on the mirror.
 7. The apparatus of claim 1, wherein, when in use,the mirror oscillates with a sinusoidal motion.
 8. The apparatus ofclaim 7, wherein, when in use, the pulses of the radiation systemsubstantially correspond in timing to a zero crossing of the sinusoidalmotion of the mirror oscillation.
 9. The apparatus of claim 1, whereinthe mirror is substantially planar.
 10. The apparatus of claim 1,wherein the mirror is located proximate a pupil plane of the projectionsystem, or a conjugate plane thereof.
 11. The apparatus of claim 1,wherein the mirror is located at a conjugate plane of a pupil plane ofthe projection system.
 12. The apparatus of claim 1, wherein thepositioning structure is configured to move the substrate at asubstantially constant velocity relative to the projection system duringa plurality of pulses of the radiation beam and during intervalstherebetween, and wherein the patterned radiation beam is moved insynchronism with the movement of the substrate for a duration of atleast one pulse of the radiation beam.
 13. The apparatus of claim 1,wherein the patterned radiation beam is scanned in synchronism with themovement of the substrate during a plurality of pulses of the radiationbeam, such that a pattern of the programmable patterning structure isprojected onto substantially a same place on the substrate a pluralityof times.
 14. The apparatus of claim 1, wherein a configuration of theprogrammable patterning structure is changed between the plurality ofprojections that are directed onto substantially the same place on thesubstrate.
 15. The lithographic projection apparatus according to claim13, wherein (i) an intensity of the patterned radiation beam, (ii) anillumination of the programmable patterning structure, (iii) a pupilfiltering, or any combination of (i) to (iii), are changed for at leastone of the plurality of projections that are directed onto substantiallythe same place on the substrate.
 16. A device manufacturing method,comprising: providing a pulsed beam of radiation; patterning the pulsedbeam according to a desired pattern to generate a patterned radiationbeam; projecting the patterned radiation beam onto a target portion of alayer of radiation-sensitive material that at least partially covers asubstrate; moving the substrate relative to a projection system thatprojects the patterned radiation beam onto the substrate duringexposure; and oscillatingly pivoting a single-faceted pivotable mirroraccording to an oscillation timing that substantially corresponds to apulse frequency of the radiation beam, thereby altering a path of thepatterned radiation beam relative to the projection system during atleast one pulse of the radiation beam, wherein the path is altered insynchronism with the movement of the substrate during the at least onepulse and wherein a cross-section of the patterned radiation beam isprojected onto a plane parallel to a surface of the target portion ofthe substrate.
 17. The method of claim 16, wherein moving the substrateincludes moving the substrate at a substantially constant velocityrelative to the projection system during a plurality of pulses of theradiation beam and during intervals therebetween, and wherein the pathis altered in synchronism with the movement of the substrate for aduration of at least one pulse of the radiation beam.
 18. The method ofclaim 16, further comprising altering the path of the patternedradiation beam in synchronism with the movement of the substrate duringa plurality of pulses of the radiation beam, such that a pattern of theprogrammable patterning structure is projected onto substantially a sameplace on the substrate a plurality of times.
 19. The method of claim 18,further comprising changing a configuration of the programmablepatterning structure between the plurality of projections that aredirected onto substantially the same place on the substrate.
 20. Themethod of claim 18, further comprising changing (i) an intensity of thepatterned radiation beam, (ii) an illumination of the programmablepatterning structure, (iii) a pupil filtering, or any combination of (i)to (iii), for at least one of the plurality of projections that aredirected onto substantially the same place on the substrate.
 21. Themethod of claim 16, wherein the mirror oscillates with a sinusoidalmotion.
 22. The method of claim 21, wherein pulses of the pulsed beamsubstantially correspond in timing to zero crossings of the sinusoidalmotion of the mirror oscillation.
 23. An apparatus comprising aprojection system, said projection system having: a single-facetedoscillatingly pivotable mirror, and an actuator functionally connectedto said pivotable mirror, said actuator being configured tooscillatingly pivot the mirror.
 24. The apparatus of claim 23, whereinsaid pivotable mirror is positioned in the pupil plane of an opticalsystem.
 25. The apparatus of claim 23, wherein said actuator isconfigured to oscillate the mirror at a frequency in the range of 1-10kHz.
 26. The apparatus of claim 23, further comprising a radiationsource, and a patterning device constructed and arranged to receive aradiation beam provided by said radiation source and to pattern theradiation beam.
 27. The apparatus of claim 26, wherein said patterningdevice is a programmable patterning device.